Home bits in ID overflow at scale

[rbuch]

When running at scale (288 nodes with 128 PEs per node), I am observing assertion failures in creating IDs. I'm 99% sure the issue is being caused by the CkLocMgr::homePe function returning an int, which is then getting shifted up to something negative and then converted into a CmiUInt8, which is then causing it to have an (invalid) value too large for its space in the 64-bit ID. I have a patch that should fix this, I'll create a PR for it when my test job runs and confirms that it actually works.